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<pre><span class="sourceLineNo">001</span>/*<a name="line.1"></a>
<span class="sourceLineNo">002</span> * Copyright (C) 2008 The Guava Authors<a name="line.2"></a>
<span class="sourceLineNo">003</span> *<a name="line.3"></a>
<span class="sourceLineNo">004</span> * Licensed under the Apache License, Version 2.0 (the "License");<a name="line.4"></a>
<span class="sourceLineNo">005</span> * you may not use this file except in compliance with the License.<a name="line.5"></a>
<span class="sourceLineNo">006</span> * You may obtain a copy of the License at<a name="line.6"></a>
<span class="sourceLineNo">007</span> *<a name="line.7"></a>
<span class="sourceLineNo">008</span> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.8"></a>
<span class="sourceLineNo">009</span> *<a name="line.9"></a>
<span class="sourceLineNo">010</span> * Unless required by applicable law or agreed to in writing, software<a name="line.10"></a>
<span class="sourceLineNo">011</span> * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.11"></a>
<span class="sourceLineNo">012</span> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.12"></a>
<span class="sourceLineNo">013</span> * See the License for the specific language governing permissions and<a name="line.13"></a>
<span class="sourceLineNo">014</span> * limitations under the License.<a name="line.14"></a>
<span class="sourceLineNo">015</span> */<a name="line.15"></a>
<span class="sourceLineNo">016</span><a name="line.16"></a>
<span class="sourceLineNo">017</span>package com.google.common.collect;<a name="line.17"></a>
<span class="sourceLineNo">018</span><a name="line.18"></a>
<span class="sourceLineNo">019</span>import static com.google.common.base.Preconditions.checkArgument;<a name="line.19"></a>
<span class="sourceLineNo">020</span>import static com.google.common.base.Preconditions.checkNotNull;<a name="line.20"></a>
<span class="sourceLineNo">021</span>import static com.google.common.math.LongMath.binomial;<a name="line.21"></a>
<span class="sourceLineNo">022</span><a name="line.22"></a>
<span class="sourceLineNo">023</span>import com.google.common.annotations.Beta;<a name="line.23"></a>
<span class="sourceLineNo">024</span>import com.google.common.annotations.GwtCompatible;<a name="line.24"></a>
<span class="sourceLineNo">025</span>import com.google.common.base.Function;<a name="line.25"></a>
<span class="sourceLineNo">026</span>import com.google.common.base.Joiner;<a name="line.26"></a>
<span class="sourceLineNo">027</span>import com.google.common.base.Predicate;<a name="line.27"></a>
<span class="sourceLineNo">028</span>import com.google.common.base.Predicates;<a name="line.28"></a>
<span class="sourceLineNo">029</span>import com.google.common.math.IntMath;<a name="line.29"></a>
<span class="sourceLineNo">030</span>import com.google.common.primitives.Ints;<a name="line.30"></a>
<span class="sourceLineNo">031</span><a name="line.31"></a>
<span class="sourceLineNo">032</span>import java.util.AbstractCollection;<a name="line.32"></a>
<span class="sourceLineNo">033</span>import java.util.ArrayList;<a name="line.33"></a>
<span class="sourceLineNo">034</span>import java.util.Collection;<a name="line.34"></a>
<span class="sourceLineNo">035</span>import java.util.Collections;<a name="line.35"></a>
<span class="sourceLineNo">036</span>import java.util.Comparator;<a name="line.36"></a>
<span class="sourceLineNo">037</span>import java.util.Iterator;<a name="line.37"></a>
<span class="sourceLineNo">038</span>import java.util.List;<a name="line.38"></a>
<span class="sourceLineNo">039</span><a name="line.39"></a>
<span class="sourceLineNo">040</span>import javax.annotation.Nullable;<a name="line.40"></a>
<span class="sourceLineNo">041</span><a name="line.41"></a>
<span class="sourceLineNo">042</span>/**<a name="line.42"></a>
<span class="sourceLineNo">043</span> * Provides static methods for working with {@code Collection} instances.<a name="line.43"></a>
<span class="sourceLineNo">044</span> *<a name="line.44"></a>
<span class="sourceLineNo">045</span> * @author Chris Povirk<a name="line.45"></a>
<span class="sourceLineNo">046</span> * @author Mike Bostock<a name="line.46"></a>
<span class="sourceLineNo">047</span> * @author Jared Levy<a name="line.47"></a>
<span class="sourceLineNo">048</span> * @since 2.0 (imported from Google Collections Library)<a name="line.48"></a>
<span class="sourceLineNo">049</span> */<a name="line.49"></a>
<span class="sourceLineNo">050</span>@GwtCompatible<a name="line.50"></a>
<span class="sourceLineNo">051</span>public final class Collections2 {<a name="line.51"></a>
<span class="sourceLineNo">052</span>  private Collections2() {}<a name="line.52"></a>
<span class="sourceLineNo">053</span><a name="line.53"></a>
<span class="sourceLineNo">054</span>  /**<a name="line.54"></a>
<span class="sourceLineNo">055</span>   * Returns the elements of {@code unfiltered} that satisfy a predicate. The<a name="line.55"></a>
<span class="sourceLineNo">056</span>   * returned collection is a live view of {@code unfiltered}; changes to one<a name="line.56"></a>
<span class="sourceLineNo">057</span>   * affect the other.<a name="line.57"></a>
<span class="sourceLineNo">058</span>   *<a name="line.58"></a>
<span class="sourceLineNo">059</span>   * &lt;p&gt;The resulting collection's iterator does not support {@code remove()},<a name="line.59"></a>
<span class="sourceLineNo">060</span>   * but all other collection methods are supported. When given an element that<a name="line.60"></a>
<span class="sourceLineNo">061</span>   * doesn't satisfy the predicate, the collection's {@code add()} and {@code<a name="line.61"></a>
<span class="sourceLineNo">062</span>   * addAll()} methods throw an {@link IllegalArgumentException}. When methods<a name="line.62"></a>
<span class="sourceLineNo">063</span>   * such as {@code removeAll()} and {@code clear()} are called on the filtered<a name="line.63"></a>
<span class="sourceLineNo">064</span>   * collection, only elements that satisfy the filter will be removed from the<a name="line.64"></a>
<span class="sourceLineNo">065</span>   * underlying collection.<a name="line.65"></a>
<span class="sourceLineNo">066</span>   *<a name="line.66"></a>
<span class="sourceLineNo">067</span>   * &lt;p&gt;The returned collection isn't threadsafe or serializable, even if<a name="line.67"></a>
<span class="sourceLineNo">068</span>   * {@code unfiltered} is.<a name="line.68"></a>
<span class="sourceLineNo">069</span>   *<a name="line.69"></a>
<span class="sourceLineNo">070</span>   * &lt;p&gt;Many of the filtered collection's methods, such as {@code size()},<a name="line.70"></a>
<span class="sourceLineNo">071</span>   * iterate across every element in the underlying collection and determine<a name="line.71"></a>
<span class="sourceLineNo">072</span>   * which elements satisfy the filter. When a live view is &lt;i&gt;not&lt;/i&gt; needed,<a name="line.72"></a>
<span class="sourceLineNo">073</span>   * it may be faster to copy {@code Iterables.filter(unfiltered, predicate)}<a name="line.73"></a>
<span class="sourceLineNo">074</span>   * and use the copy.<a name="line.74"></a>
<span class="sourceLineNo">075</span>   *<a name="line.75"></a>
<span class="sourceLineNo">076</span>   * &lt;p&gt;&lt;b&gt;Warning:&lt;/b&gt; {@code predicate} must be &lt;i&gt;consistent with equals&lt;/i&gt;,<a name="line.76"></a>
<span class="sourceLineNo">077</span>   * as documented at {@link Predicate#apply}. Do not provide a predicate such<a name="line.77"></a>
<span class="sourceLineNo">078</span>   * as {@code Predicates.instanceOf(ArrayList.class)}, which is inconsistent<a name="line.78"></a>
<span class="sourceLineNo">079</span>   * with equals. (See {@link Iterables#filter(Iterable, Class)} for related<a name="line.79"></a>
<span class="sourceLineNo">080</span>   * functionality.)<a name="line.80"></a>
<span class="sourceLineNo">081</span>   */<a name="line.81"></a>
<span class="sourceLineNo">082</span>  // TODO(kevinb): how can we omit that Iterables link when building gwt<a name="line.82"></a>
<span class="sourceLineNo">083</span>  // javadoc?<a name="line.83"></a>
<span class="sourceLineNo">084</span>  public static &lt;E&gt; Collection&lt;E&gt; filter(<a name="line.84"></a>
<span class="sourceLineNo">085</span>      Collection&lt;E&gt; unfiltered, Predicate&lt;? super E&gt; predicate) {<a name="line.85"></a>
<span class="sourceLineNo">086</span>    if (unfiltered instanceof FilteredCollection) {<a name="line.86"></a>
<span class="sourceLineNo">087</span>      // Support clear(), removeAll(), and retainAll() when filtering a filtered<a name="line.87"></a>
<span class="sourceLineNo">088</span>      // collection.<a name="line.88"></a>
<span class="sourceLineNo">089</span>      return ((FilteredCollection&lt;E&gt;) unfiltered).createCombined(predicate);<a name="line.89"></a>
<span class="sourceLineNo">090</span>    }<a name="line.90"></a>
<span class="sourceLineNo">091</span><a name="line.91"></a>
<span class="sourceLineNo">092</span>    return new FilteredCollection&lt;E&gt;(<a name="line.92"></a>
<span class="sourceLineNo">093</span>        checkNotNull(unfiltered), checkNotNull(predicate));<a name="line.93"></a>
<span class="sourceLineNo">094</span>  }<a name="line.94"></a>
<span class="sourceLineNo">095</span><a name="line.95"></a>
<span class="sourceLineNo">096</span>  /**<a name="line.96"></a>
<span class="sourceLineNo">097</span>   * Delegates to {@link Collection#contains}. Returns {@code false} if the<a name="line.97"></a>
<span class="sourceLineNo">098</span>   * {@code contains} method throws a {@code ClassCastException}.<a name="line.98"></a>
<span class="sourceLineNo">099</span>   */<a name="line.99"></a>
<span class="sourceLineNo">100</span>  static boolean safeContains(Collection&lt;?&gt; collection, Object object) {<a name="line.100"></a>
<span class="sourceLineNo">101</span>    try {<a name="line.101"></a>
<span class="sourceLineNo">102</span>      return collection.contains(object);<a name="line.102"></a>
<span class="sourceLineNo">103</span>    } catch (ClassCastException e) {<a name="line.103"></a>
<span class="sourceLineNo">104</span>      return false;<a name="line.104"></a>
<span class="sourceLineNo">105</span>    }<a name="line.105"></a>
<span class="sourceLineNo">106</span>  }<a name="line.106"></a>
<span class="sourceLineNo">107</span><a name="line.107"></a>
<span class="sourceLineNo">108</span>  static class FilteredCollection&lt;E&gt; implements Collection&lt;E&gt; {<a name="line.108"></a>
<span class="sourceLineNo">109</span>    final Collection&lt;E&gt; unfiltered;<a name="line.109"></a>
<span class="sourceLineNo">110</span>    final Predicate&lt;? super E&gt; predicate;<a name="line.110"></a>
<span class="sourceLineNo">111</span><a name="line.111"></a>
<span class="sourceLineNo">112</span>    FilteredCollection(Collection&lt;E&gt; unfiltered,<a name="line.112"></a>
<span class="sourceLineNo">113</span>        Predicate&lt;? super E&gt; predicate) {<a name="line.113"></a>
<span class="sourceLineNo">114</span>      this.unfiltered = unfiltered;<a name="line.114"></a>
<span class="sourceLineNo">115</span>      this.predicate = predicate;<a name="line.115"></a>
<span class="sourceLineNo">116</span>    }<a name="line.116"></a>
<span class="sourceLineNo">117</span><a name="line.117"></a>
<span class="sourceLineNo">118</span>    FilteredCollection&lt;E&gt; createCombined(Predicate&lt;? super E&gt; newPredicate) {<a name="line.118"></a>
<span class="sourceLineNo">119</span>      return new FilteredCollection&lt;E&gt;(unfiltered,<a name="line.119"></a>
<span class="sourceLineNo">120</span>          Predicates.&lt;E&gt;and(predicate, newPredicate));<a name="line.120"></a>
<span class="sourceLineNo">121</span>      // .&lt;E&gt; above needed to compile in JDK 5<a name="line.121"></a>
<span class="sourceLineNo">122</span>    }<a name="line.122"></a>
<span class="sourceLineNo">123</span><a name="line.123"></a>
<span class="sourceLineNo">124</span>    @Override<a name="line.124"></a>
<span class="sourceLineNo">125</span>    public boolean add(E element) {<a name="line.125"></a>
<span class="sourceLineNo">126</span>      checkArgument(predicate.apply(element));<a name="line.126"></a>
<span class="sourceLineNo">127</span>      return unfiltered.add(element);<a name="line.127"></a>
<span class="sourceLineNo">128</span>    }<a name="line.128"></a>
<span class="sourceLineNo">129</span><a name="line.129"></a>
<span class="sourceLineNo">130</span>    @Override<a name="line.130"></a>
<span class="sourceLineNo">131</span>    public boolean addAll(Collection&lt;? extends E&gt; collection) {<a name="line.131"></a>
<span class="sourceLineNo">132</span>      for (E element : collection) {<a name="line.132"></a>
<span class="sourceLineNo">133</span>        checkArgument(predicate.apply(element));<a name="line.133"></a>
<span class="sourceLineNo">134</span>      }<a name="line.134"></a>
<span class="sourceLineNo">135</span>      return unfiltered.addAll(collection);<a name="line.135"></a>
<span class="sourceLineNo">136</span>    }<a name="line.136"></a>
<span class="sourceLineNo">137</span><a name="line.137"></a>
<span class="sourceLineNo">138</span>    @Override<a name="line.138"></a>
<span class="sourceLineNo">139</span>    public void clear() {<a name="line.139"></a>
<span class="sourceLineNo">140</span>      Iterables.removeIf(unfiltered, predicate);<a name="line.140"></a>
<span class="sourceLineNo">141</span>    }<a name="line.141"></a>
<span class="sourceLineNo">142</span><a name="line.142"></a>
<span class="sourceLineNo">143</span>    @Override<a name="line.143"></a>
<span class="sourceLineNo">144</span>    public boolean contains(Object element) {<a name="line.144"></a>
<span class="sourceLineNo">145</span>      try {<a name="line.145"></a>
<span class="sourceLineNo">146</span>        // unsafe cast can result in a CCE from predicate.apply(), which we<a name="line.146"></a>
<span class="sourceLineNo">147</span>        // will catch<a name="line.147"></a>
<span class="sourceLineNo">148</span>        @SuppressWarnings("unchecked")<a name="line.148"></a>
<span class="sourceLineNo">149</span>        E e = (E) element;<a name="line.149"></a>
<span class="sourceLineNo">150</span><a name="line.150"></a>
<span class="sourceLineNo">151</span>        /*<a name="line.151"></a>
<span class="sourceLineNo">152</span>         * We check whether e satisfies the predicate, when we really mean to<a name="line.152"></a>
<span class="sourceLineNo">153</span>         * check whether the element contained in the set does. This is ok as<a name="line.153"></a>
<span class="sourceLineNo">154</span>         * long as the predicate is consistent with equals, as required.<a name="line.154"></a>
<span class="sourceLineNo">155</span>         */<a name="line.155"></a>
<span class="sourceLineNo">156</span>        return predicate.apply(e) &amp;&amp; unfiltered.contains(element);<a name="line.156"></a>
<span class="sourceLineNo">157</span>      } catch (NullPointerException e) {<a name="line.157"></a>
<span class="sourceLineNo">158</span>        return false;<a name="line.158"></a>
<span class="sourceLineNo">159</span>      } catch (ClassCastException e) {<a name="line.159"></a>
<span class="sourceLineNo">160</span>        return false;<a name="line.160"></a>
<span class="sourceLineNo">161</span>      }<a name="line.161"></a>
<span class="sourceLineNo">162</span>    }<a name="line.162"></a>
<span class="sourceLineNo">163</span><a name="line.163"></a>
<span class="sourceLineNo">164</span>    @Override<a name="line.164"></a>
<span class="sourceLineNo">165</span>    public boolean containsAll(Collection&lt;?&gt; collection) {<a name="line.165"></a>
<span class="sourceLineNo">166</span>      for (Object element : collection) {<a name="line.166"></a>
<span class="sourceLineNo">167</span>        if (!contains(element)) {<a name="line.167"></a>
<span class="sourceLineNo">168</span>          return false;<a name="line.168"></a>
<span class="sourceLineNo">169</span>        }<a name="line.169"></a>
<span class="sourceLineNo">170</span>      }<a name="line.170"></a>
<span class="sourceLineNo">171</span>      return true;<a name="line.171"></a>
<span class="sourceLineNo">172</span>    }<a name="line.172"></a>
<span class="sourceLineNo">173</span><a name="line.173"></a>
<span class="sourceLineNo">174</span>    @Override<a name="line.174"></a>
<span class="sourceLineNo">175</span>    public boolean isEmpty() {<a name="line.175"></a>
<span class="sourceLineNo">176</span>      return !Iterators.any(unfiltered.iterator(), predicate);<a name="line.176"></a>
<span class="sourceLineNo">177</span>    }<a name="line.177"></a>
<span class="sourceLineNo">178</span><a name="line.178"></a>
<span class="sourceLineNo">179</span>    @Override<a name="line.179"></a>
<span class="sourceLineNo">180</span>    public Iterator&lt;E&gt; iterator() {<a name="line.180"></a>
<span class="sourceLineNo">181</span>      return Iterators.filter(unfiltered.iterator(), predicate);<a name="line.181"></a>
<span class="sourceLineNo">182</span>    }<a name="line.182"></a>
<span class="sourceLineNo">183</span><a name="line.183"></a>
<span class="sourceLineNo">184</span>    @Override<a name="line.184"></a>
<span class="sourceLineNo">185</span>    public boolean remove(Object element) {<a name="line.185"></a>
<span class="sourceLineNo">186</span>      try {<a name="line.186"></a>
<span class="sourceLineNo">187</span>        // unsafe cast can result in a CCE from predicate.apply(), which we<a name="line.187"></a>
<span class="sourceLineNo">188</span>        // will catch<a name="line.188"></a>
<span class="sourceLineNo">189</span>        @SuppressWarnings("unchecked")<a name="line.189"></a>
<span class="sourceLineNo">190</span>        E e = (E) element;<a name="line.190"></a>
<span class="sourceLineNo">191</span><a name="line.191"></a>
<span class="sourceLineNo">192</span>        // See comment in contains() concerning predicate.apply(e)<a name="line.192"></a>
<span class="sourceLineNo">193</span>        return predicate.apply(e) &amp;&amp; unfiltered.remove(element);<a name="line.193"></a>
<span class="sourceLineNo">194</span>      } catch (NullPointerException e) {<a name="line.194"></a>
<span class="sourceLineNo">195</span>        return false;<a name="line.195"></a>
<span class="sourceLineNo">196</span>      } catch (ClassCastException e) {<a name="line.196"></a>
<span class="sourceLineNo">197</span>        return false;<a name="line.197"></a>
<span class="sourceLineNo">198</span>      }<a name="line.198"></a>
<span class="sourceLineNo">199</span>    }<a name="line.199"></a>
<span class="sourceLineNo">200</span><a name="line.200"></a>
<span class="sourceLineNo">201</span>    @Override<a name="line.201"></a>
<span class="sourceLineNo">202</span>    public boolean removeAll(final Collection&lt;?&gt; collection) {<a name="line.202"></a>
<span class="sourceLineNo">203</span>      checkNotNull(collection);<a name="line.203"></a>
<span class="sourceLineNo">204</span>      Predicate&lt;E&gt; combinedPredicate = new Predicate&lt;E&gt;() {<a name="line.204"></a>
<span class="sourceLineNo">205</span>        @Override<a name="line.205"></a>
<span class="sourceLineNo">206</span>        public boolean apply(E input) {<a name="line.206"></a>
<span class="sourceLineNo">207</span>          return predicate.apply(input) &amp;&amp; collection.contains(input);<a name="line.207"></a>
<span class="sourceLineNo">208</span>        }<a name="line.208"></a>
<span class="sourceLineNo">209</span>      };<a name="line.209"></a>
<span class="sourceLineNo">210</span>      return Iterables.removeIf(unfiltered, combinedPredicate);<a name="line.210"></a>
<span class="sourceLineNo">211</span>    }<a name="line.211"></a>
<span class="sourceLineNo">212</span><a name="line.212"></a>
<span class="sourceLineNo">213</span>    @Override<a name="line.213"></a>
<span class="sourceLineNo">214</span>    public boolean retainAll(final Collection&lt;?&gt; collection) {<a name="line.214"></a>
<span class="sourceLineNo">215</span>      checkNotNull(collection);<a name="line.215"></a>
<span class="sourceLineNo">216</span>      Predicate&lt;E&gt; combinedPredicate = new Predicate&lt;E&gt;() {<a name="line.216"></a>
<span class="sourceLineNo">217</span>        @Override<a name="line.217"></a>
<span class="sourceLineNo">218</span>        public boolean apply(E input) {<a name="line.218"></a>
<span class="sourceLineNo">219</span>          // See comment in contains() concerning predicate.apply(e)<a name="line.219"></a>
<span class="sourceLineNo">220</span>          return predicate.apply(input) &amp;&amp; !collection.contains(input);<a name="line.220"></a>
<span class="sourceLineNo">221</span>        }<a name="line.221"></a>
<span class="sourceLineNo">222</span>      };<a name="line.222"></a>
<span class="sourceLineNo">223</span>      return Iterables.removeIf(unfiltered, combinedPredicate);<a name="line.223"></a>
<span class="sourceLineNo">224</span>    }<a name="line.224"></a>
<span class="sourceLineNo">225</span><a name="line.225"></a>
<span class="sourceLineNo">226</span>    @Override<a name="line.226"></a>
<span class="sourceLineNo">227</span>    public int size() {<a name="line.227"></a>
<span class="sourceLineNo">228</span>      return Iterators.size(iterator());<a name="line.228"></a>
<span class="sourceLineNo">229</span>    }<a name="line.229"></a>
<span class="sourceLineNo">230</span><a name="line.230"></a>
<span class="sourceLineNo">231</span>    @Override<a name="line.231"></a>
<span class="sourceLineNo">232</span>    public Object[] toArray() {<a name="line.232"></a>
<span class="sourceLineNo">233</span>      // creating an ArrayList so filtering happens once<a name="line.233"></a>
<span class="sourceLineNo">234</span>      return Lists.newArrayList(iterator()).toArray();<a name="line.234"></a>
<span class="sourceLineNo">235</span>    }<a name="line.235"></a>
<span class="sourceLineNo">236</span><a name="line.236"></a>
<span class="sourceLineNo">237</span>    @Override<a name="line.237"></a>
<span class="sourceLineNo">238</span>    public &lt;T&gt; T[] toArray(T[] array) {<a name="line.238"></a>
<span class="sourceLineNo">239</span>      return Lists.newArrayList(iterator()).toArray(array);<a name="line.239"></a>
<span class="sourceLineNo">240</span>    }<a name="line.240"></a>
<span class="sourceLineNo">241</span><a name="line.241"></a>
<span class="sourceLineNo">242</span>    @Override public String toString() {<a name="line.242"></a>
<span class="sourceLineNo">243</span>      return Iterators.toString(iterator());<a name="line.243"></a>
<span class="sourceLineNo">244</span>    }<a name="line.244"></a>
<span class="sourceLineNo">245</span>  }<a name="line.245"></a>
<span class="sourceLineNo">246</span><a name="line.246"></a>
<span class="sourceLineNo">247</span>  /**<a name="line.247"></a>
<span class="sourceLineNo">248</span>   * Returns a collection that applies {@code function} to each element of<a name="line.248"></a>
<span class="sourceLineNo">249</span>   * {@code fromCollection}. The returned collection is a live view of {@code<a name="line.249"></a>
<span class="sourceLineNo">250</span>   * fromCollection}; changes to one affect the other.<a name="line.250"></a>
<span class="sourceLineNo">251</span>   *<a name="line.251"></a>
<span class="sourceLineNo">252</span>   * &lt;p&gt;The returned collection's {@code add()} and {@code addAll()} methods<a name="line.252"></a>
<span class="sourceLineNo">253</span>   * throw an {@link UnsupportedOperationException}. All other collection<a name="line.253"></a>
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<span class="sourceLineNo">255</span>   *<a name="line.255"></a>
<span class="sourceLineNo">256</span>   * &lt;p&gt;The returned collection isn't threadsafe or serializable, even if<a name="line.256"></a>
<span class="sourceLineNo">257</span>   * {@code fromCollection} is.<a name="line.257"></a>
<span class="sourceLineNo">258</span>   *<a name="line.258"></a>
<span class="sourceLineNo">259</span>   * &lt;p&gt;When a live view is &lt;i&gt;not&lt;/i&gt; needed, it may be faster to copy the<a name="line.259"></a>
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<span class="sourceLineNo">261</span>   *<a name="line.261"></a>
<span class="sourceLineNo">262</span>   * &lt;p&gt;If the input {@code Collection} is known to be a {@code List}, consider<a name="line.262"></a>
<span class="sourceLineNo">263</span>   * {@link Lists#transform}. If only an {@code Iterable} is available, use<a name="line.263"></a>
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<span class="sourceLineNo">298</span>  /**<a name="line.298"></a>
<span class="sourceLineNo">299</span>   * Returns {@code true} if the collection {@code self} contains all of the<a name="line.299"></a>
<span class="sourceLineNo">300</span>   * elements in the collection {@code c}.<a name="line.300"></a>
<span class="sourceLineNo">301</span>   *<a name="line.301"></a>
<span class="sourceLineNo">302</span>   * &lt;p&gt;This method iterates over the specified collection {@code c}, checking<a name="line.302"></a>
<span class="sourceLineNo">303</span>   * each element returned by the iterator in turn to see if it is contained in<a name="line.303"></a>
<span class="sourceLineNo">304</span>   * the specified collection {@code self}. If all elements are so contained,<a name="line.304"></a>
<span class="sourceLineNo">305</span>   * {@code true} is returned, otherwise {@code false}.<a name="line.305"></a>
<span class="sourceLineNo">306</span>   *<a name="line.306"></a>
<span class="sourceLineNo">307</span>   * @param self a collection which might contain all elements in {@code c}<a name="line.307"></a>
<span class="sourceLineNo">308</span>   * @param c a collection whose elements might be contained by {@code self}<a name="line.308"></a>
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<span class="sourceLineNo">321</span>   * An implementation of {@link Collection#toString()}.<a name="line.321"></a>
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<span class="sourceLineNo">325</span>        = newStringBuilderForCollection(collection.size()).append('[');<a name="line.325"></a>
<span class="sourceLineNo">326</span>    STANDARD_JOINER.appendTo(<a name="line.326"></a>
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<span class="sourceLineNo">343</span>  /**<a name="line.343"></a>
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<span class="sourceLineNo">351</span><a name="line.351"></a>
<span class="sourceLineNo">352</span>  /**<a name="line.352"></a>
<span class="sourceLineNo">353</span>   * Returns a {@link Collection} of all the permutations of the specified<a name="line.353"></a>
<span class="sourceLineNo">354</span>   * {@link Iterable}.<a name="line.354"></a>
<span class="sourceLineNo">355</span>   *<a name="line.355"></a>
<span class="sourceLineNo">356</span>   * &lt;p&gt;&lt;i&gt;Notes:&lt;/i&gt; This is an implementation of the algorithm for<a name="line.356"></a>
<span class="sourceLineNo">357</span>   * Lexicographical Permutations Generation, described in Knuth's "The Art of<a name="line.357"></a>
<span class="sourceLineNo">358</span>   * Computer Programming", Volume 4, Chapter 7, Section 7.2.1.2. The<a name="line.358"></a>
<span class="sourceLineNo">359</span>   * iteration order follows the lexicographical order. This means that<a name="line.359"></a>
<span class="sourceLineNo">360</span>   * the first permutation will be in ascending order, and the last will be in<a name="line.360"></a>
<span class="sourceLineNo">361</span>   * descending order.<a name="line.361"></a>
<span class="sourceLineNo">362</span>   *<a name="line.362"></a>
<span class="sourceLineNo">363</span>   * &lt;p&gt;Duplicate elements are considered equal. For example, the list [1, 1]<a name="line.363"></a>
<span class="sourceLineNo">364</span>   * will have only one permutation, instead of two. This is why the elements<a name="line.364"></a>
<span class="sourceLineNo">365</span>   * have to implement {@link Comparable}.<a name="line.365"></a>
<span class="sourceLineNo">366</span>   *<a name="line.366"></a>
<span class="sourceLineNo">367</span>   * &lt;p&gt;An empty iterable has only one permutation, which is an empty list.<a name="line.367"></a>
<span class="sourceLineNo">368</span>   *<a name="line.368"></a>
<span class="sourceLineNo">369</span>   * &lt;p&gt;This method is equivalent to<a name="line.369"></a>
<span class="sourceLineNo">370</span>   * {@code Collections2.orderedPermutations(list, Ordering.natural())}.<a name="line.370"></a>
<span class="sourceLineNo">371</span>   *<a name="line.371"></a>
<span class="sourceLineNo">372</span>   * @param elements the original iterable whose elements have to be permuted.<a name="line.372"></a>
<span class="sourceLineNo">373</span>   * @return an immutable {@link Collection} containing all the different<a name="line.373"></a>
<span class="sourceLineNo">374</span>   *     permutations of the original iterable.<a name="line.374"></a>
<span class="sourceLineNo">375</span>   * @throws NullPointerException if the specified iterable is null or has any<a name="line.375"></a>
<span class="sourceLineNo">376</span>   *     null elements.<a name="line.376"></a>
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<span class="sourceLineNo">383</span><a name="line.383"></a>
<span class="sourceLineNo">384</span>  /**<a name="line.384"></a>
<span class="sourceLineNo">385</span>   * Returns a {@link Collection} of all the permutations of the specified<a name="line.385"></a>
<span class="sourceLineNo">386</span>   * {@link Iterable} using the specified {@link Comparator} for establishing<a name="line.386"></a>
<span class="sourceLineNo">387</span>   * the lexicographical ordering.<a name="line.387"></a>
<span class="sourceLineNo">388</span>   *<a name="line.388"></a>
<span class="sourceLineNo">389</span>   * &lt;p&gt;Examples: &lt;pre&gt;   {@code<a name="line.389"></a>
<span class="sourceLineNo">390</span>   *<a name="line.390"></a>
<span class="sourceLineNo">391</span>   *   for (List&lt;String&gt; perm : orderedPermutations(asList("b", "c", "a"))) {<a name="line.391"></a>
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<span class="sourceLineNo">394</span>   *   // -&gt; ["a", "b", "c"]<a name="line.394"></a>
<span class="sourceLineNo">395</span>   *   // -&gt; ["a", "c", "b"]<a name="line.395"></a>
<span class="sourceLineNo">396</span>   *   // -&gt; ["b", "a", "c"]<a name="line.396"></a>
<span class="sourceLineNo">397</span>   *   // -&gt; ["b", "c", "a"]<a name="line.397"></a>
<span class="sourceLineNo">398</span>   *   // -&gt; ["c", "a", "b"]<a name="line.398"></a>
<span class="sourceLineNo">399</span>   *   // -&gt; ["c", "b", "a"]<a name="line.399"></a>
<span class="sourceLineNo">400</span>   *<a name="line.400"></a>
<span class="sourceLineNo">401</span>   *   for (List&lt;Integer&gt; perm : orderedPermutations(asList(1, 2, 2, 1))) {<a name="line.401"></a>
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<span class="sourceLineNo">404</span>   *   // -&gt; [1, 1, 2, 2]<a name="line.404"></a>
<span class="sourceLineNo">405</span>   *   // -&gt; [1, 2, 1, 2]<a name="line.405"></a>
<span class="sourceLineNo">406</span>   *   // -&gt; [1, 2, 2, 1]<a name="line.406"></a>
<span class="sourceLineNo">407</span>   *   // -&gt; [2, 1, 1, 2]<a name="line.407"></a>
<span class="sourceLineNo">408</span>   *   // -&gt; [2, 1, 2, 1]<a name="line.408"></a>
<span class="sourceLineNo">409</span>   *   // -&gt; [2, 2, 1, 1]}&lt;/pre&gt;<a name="line.409"></a>
<span class="sourceLineNo">410</span>   *<a name="line.410"></a>
<span class="sourceLineNo">411</span>   * &lt;p&gt;&lt;i&gt;Notes:&lt;/i&gt; This is an implementation of the algorithm for<a name="line.411"></a>
<span class="sourceLineNo">412</span>   * Lexicographical Permutations Generation, described in Knuth's "The Art of<a name="line.412"></a>
<span class="sourceLineNo">413</span>   * Computer Programming", Volume 4, Chapter 7, Section 7.2.1.2. The<a name="line.413"></a>
<span class="sourceLineNo">414</span>   * iteration order follows the lexicographical order. This means that<a name="line.414"></a>
<span class="sourceLineNo">415</span>   * the first permutation will be in ascending order, and the last will be in<a name="line.415"></a>
<span class="sourceLineNo">416</span>   * descending order.<a name="line.416"></a>
<span class="sourceLineNo">417</span>   *<a name="line.417"></a>
<span class="sourceLineNo">418</span>   * &lt;p&gt;Elements that compare equal are considered equal and no new permutations<a name="line.418"></a>
<span class="sourceLineNo">419</span>   * are created by swapping them.<a name="line.419"></a>
<span class="sourceLineNo">420</span>   *<a name="line.420"></a>
<span class="sourceLineNo">421</span>   * &lt;p&gt;An empty iterable has only one permutation, which is an empty list.<a name="line.421"></a>
<span class="sourceLineNo">422</span>   *<a name="line.422"></a>
<span class="sourceLineNo">423</span>   * @param elements the original iterable whose elements have to be permuted.<a name="line.423"></a>
<span class="sourceLineNo">424</span>   * @param comparator a comparator for the iterable's elements.<a name="line.424"></a>
<span class="sourceLineNo">425</span>   * @return an immutable {@link Collection} containing all the different<a name="line.425"></a>
<span class="sourceLineNo">426</span>   *     permutations of the original iterable.<a name="line.426"></a>
<span class="sourceLineNo">427</span>   * @throws NullPointerException If the specified iterable is null, has any<a name="line.427"></a>
<span class="sourceLineNo">428</span>   *     null elements, or if the specified comparator is null.<a name="line.428"></a>
<span class="sourceLineNo">429</span>   * @since 12.0<a name="line.429"></a>
<span class="sourceLineNo">430</span>   */<a name="line.430"></a>
<span class="sourceLineNo">431</span>  @Beta public static &lt;E&gt; Collection&lt;List&lt;E&gt;&gt; orderedPermutations(<a name="line.431"></a>
<span class="sourceLineNo">432</span>      Iterable&lt;E&gt; elements, Comparator&lt;? super E&gt; comparator) {<a name="line.432"></a>
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<span class="sourceLineNo">435</span><a name="line.435"></a>
<span class="sourceLineNo">436</span>  private static final class OrderedPermutationCollection&lt;E&gt;<a name="line.436"></a>
<span class="sourceLineNo">437</span>      extends AbstractCollection&lt;List&lt;E&gt;&gt; {<a name="line.437"></a>
<span class="sourceLineNo">438</span>    final ImmutableList&lt;E&gt; inputList;<a name="line.438"></a>
<span class="sourceLineNo">439</span>    final Comparator&lt;? super E&gt; comparator;<a name="line.439"></a>
<span class="sourceLineNo">440</span>    final int size;<a name="line.440"></a>
<span class="sourceLineNo">441</span><a name="line.441"></a>
<span class="sourceLineNo">442</span>    OrderedPermutationCollection(Iterable&lt;E&gt; input,<a name="line.442"></a>
<span class="sourceLineNo">443</span>        Comparator&lt;? super E&gt; comparator) {<a name="line.443"></a>
<span class="sourceLineNo">444</span>      this.inputList = Ordering.from(comparator).immutableSortedCopy(input);<a name="line.444"></a>
<span class="sourceLineNo">445</span>      this.comparator = comparator;<a name="line.445"></a>
<span class="sourceLineNo">446</span>      this.size = calculateSize(inputList, comparator);<a name="line.446"></a>
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<span class="sourceLineNo">448</span><a name="line.448"></a>
<span class="sourceLineNo">449</span>    /**<a name="line.449"></a>
<span class="sourceLineNo">450</span>     * The number of permutations with repeated elements is calculated as<a name="line.450"></a>
<span class="sourceLineNo">451</span>     * follows:<a name="line.451"></a>
<span class="sourceLineNo">452</span>     * &lt;ul&gt;<a name="line.452"></a>
<span class="sourceLineNo">453</span>     * &lt;li&gt;For an empty list, it is 1 (base case).&lt;/li&gt;<a name="line.453"></a>
<span class="sourceLineNo">454</span>     * &lt;li&gt;When r numbers are added to a list of n-r elements, the number of<a name="line.454"></a>
<span class="sourceLineNo">455</span>     * permutations is increased by a factor of (n choose r).&lt;/li&gt;<a name="line.455"></a>
<span class="sourceLineNo">456</span>     * &lt;/ul&gt;<a name="line.456"></a>
<span class="sourceLineNo">457</span>     */<a name="line.457"></a>
<span class="sourceLineNo">458</span>    private static &lt;E&gt; int calculateSize(<a name="line.458"></a>
<span class="sourceLineNo">459</span>        List&lt;E&gt; sortedInputList, Comparator&lt;? super E&gt; comparator) {<a name="line.459"></a>
<span class="sourceLineNo">460</span>      long permutations = 1;<a name="line.460"></a>
<span class="sourceLineNo">461</span>      int n = 1;<a name="line.461"></a>
<span class="sourceLineNo">462</span>      int r = 1;<a name="line.462"></a>
<span class="sourceLineNo">463</span>      while (n &lt; sortedInputList.size()) {<a name="line.463"></a>
<span class="sourceLineNo">464</span>        int comparison = comparator.compare(<a name="line.464"></a>
<span class="sourceLineNo">465</span>            sortedInputList.get(n - 1), sortedInputList.get(n));<a name="line.465"></a>
<span class="sourceLineNo">466</span>        if (comparison &lt; 0) {<a name="line.466"></a>
<span class="sourceLineNo">467</span>          // We move to the next non-repeated element.<a name="line.467"></a>
<span class="sourceLineNo">468</span>          permutations *= binomial(n, r);<a name="line.468"></a>
<span class="sourceLineNo">469</span>          r = 0;<a name="line.469"></a>
<span class="sourceLineNo">470</span>          if (!isPositiveInt(permutations)) {<a name="line.470"></a>
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<span class="sourceLineNo">473</span>        }<a name="line.473"></a>
<span class="sourceLineNo">474</span>        n++;<a name="line.474"></a>
<span class="sourceLineNo">475</span>        r++;<a name="line.475"></a>
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<span class="sourceLineNo">477</span>      permutations *= binomial(n, r);<a name="line.477"></a>
<span class="sourceLineNo">478</span>      if (!isPositiveInt(permutations)) {<a name="line.478"></a>
<span class="sourceLineNo">479</span>        return Integer.MAX_VALUE;<a name="line.479"></a>
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<span class="sourceLineNo">481</span>      return (int) permutations;<a name="line.481"></a>
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<span class="sourceLineNo">483</span><a name="line.483"></a>
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<span class="sourceLineNo">703</span>}<a name="line.703"></a>




























































</pre>
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